After Category 5 Cyclone Pam tore his country apart, prompting a humanitarian emergency, Vanuatu's President Baldwin Lonsdale pinned at least part of the blame for the islands' predicament on manmade global warming.

The storm, which struck with a ferocity the country had not experienced before in modern history, had sustained winds of 165 miles per hour, with gusts exceeding 200 miles per hour when it roared through the tiny country. It leveled homes and businesses, and stripped trees bare on the most populated island of Efate, including the capital of Port Vila. The death toll stood at 24 on Tuesday, but it is expected to rise as more information begins streaming in from outlying islands that have been cut off from the outside world.

“This is a very devastating cyclone … I term it a monster that has hit Vanuatu,” Lonsdale said at a U.N. disaster summit in Japan, according to The Guardian. “It is a setback for the government and for the people of Vanuatu. … All the development that has taken place has been wiped out.”

He said the cyclone seasons that the nation had experienced were the result of climate change. “We see the level of sea rise … the cyclone seasons, the warm, the rain, all this is affected,” he said.

So, is the president correct to link the devastating cyclone to global warming? Or is the tie so tenuous that it's almost nonexistent? The answer, as it often is in climate science, is far more nuanced than Vanuatu's president portrays it.

Scientists say unusually mild sea surface temperatures and added atmospheric water vapor helped the storm intensify before slamming into Vanuatu. At the same time, rising sea levels likely made the storm more damaging than it would have been just a few decades ago.

Here are the main factors to consider when analyzing the potential ties between Cyclone Pam and the warming climate.

Ocean temperatures are the main suspect

Scientists Mashable contacted said the storm intensified rapidly before hitting Vanuatu, aided by an area of unusually mild ocean waters and favorable atmospheric conditions. Ocean temperatures in the area where the cyclone intensified were up to 2 degrees Celsius above average for this time of year (3.6 degrees Fahrenheit).

Some — but not all — of the sea surface temperature anomalies in the Southwest Pacific Ocean are likely related to global warming, according to Kevin Trenberth, a climate researcher with the National Center for Atmospheric Research in Boulder, Colorado, as well as other experts.

Global sea surface temperatures, showing an area of extremely warm water near Vanuatu and Australia.

Image: NOAA/ESRL

According to Trenberth, about about 0.6 degrees Celsius, or 1.1 degrees Fahrenheit, of the ocean temperature anomalies "can be blamed on human-induced global warming" while the rest is "natural" and associated with an ongoing El Niño event in the tropical Pacific Ocean.

El Niño is a climate phenomenon that features warmer than average ocean temperatures in much of the tropical Pacific Ocean. It can alter worldwide weather patterns, including tropical cyclone seasons in the Pacific and Atlantic Oceans.

Whatever the cause, though, the warm ocean waters can supercharge storms like Cyclone Pam, as more evaporation takes place and moisture is added to the air.

"The atmosphere all around there has some 10 to 20% more moisture in it than a comparable storm in the 1970s would have had. The high sea surface temperatures and the water vapor fueled the storm and undoubtedly increased its intensity and size," Trenberth said in an email conversation. "The winds are stronger, the storm surge is greater on higher sea levels."

El Niño "has played a role here on top of global warming. But strong storms can certainly occur in that region anyway (but not this strong). The sea surface temperatures are over 86 degrees Fahrenheit for heaven's sake," he said.

An analysis of long-term trends in sea surface temperatures in the region where Cyclone Pam rapidly intensified into a Category 5 monster shows that there has been a warming trend since 1948, although there are considerable uncertainties in this data, says Michael Ventrice, an operational meteorologist at WSI Corporation in Massachusetts. He said it is not clear from the data whether the higher temperatures were a result of natural variations or human effects.

Sea surface temperature departures from average in the vicinity of Vanuatu and Australia as of March 16, 2015.

Image: WeatherbellAnalytics

"The bottom line point is that there has been a long-term warming trend observed in the location where Pam intensified," Ventrice said.

Madden and Julian...

Ventrice says Cyclone Pam "thrived" in an environment that was well-suited to explosive intensification. These environmental factors included the warm ocean waters that extended deep into the ocean, as well as a natural weather cycle known as the Madden Julian Oscillation, or MJO.

In certain instances, the MJO can encourage the air to rise, forming thunderstorms as well as tropical cyclones. Think of the MJO as a helping hand that likely aided the storm's rapid intensification.

"The MJO acts to moisten the middle and upper-levels of the atmosphere and reduce vertical wind shear, both are which parameters that are musts for intensification," Ventrice said.

Few robust trends in tropical cyclones near Vanuatu

Climate research has shown that tropical cyclones in many ocean basins are becoming stronger and lasting longer than they used to. However, the Southwest Pacific, where Cyclone Pam occurred, is not one of these areas, possibly due to the relative paucity of data there.

Kerry Emanuel, a meteorologist at MIT who is a prominent researcher examining global warming-related trends in tropical storms and hurricanes, told Mashable that not much can be said about trends in the vicinity of Vanuatu.

"Ironically, this is a part of the world where we do not observe any significant upward trends in tropical cyclone metrics, and few models predict upward trends there as a consequence of global warming," he said in an email.

In a post for the blog Realclimate on March 18, Emanuel wrote that there are signs that some parameters of severe tropical cyclones are changing, even in areas like the Southwest Pacific basin where data is relatively sparse.

"While Pam and Haiyan, as well as other recent tropical cyclone disasters, cannot be uniquely pinned on global warming, they have no doubt been influenced by natural and anthropogenic climate change and they do remind us of our continuing vulnerability to such storms," Emanuel said.

Tom Knutson, a researcher with the National Oceanic and Atmospheric Administration, says that of the six ocean basins that give rise to tropical cyclones, the Southwest Pacific basin is an area that shows the least tendency for an increase in storm activity by the end of the century. In fact, there may be a decrease in cyclone frequency or intensity there, based on the most recent computer model simulations, Knutson says.

James Elsner, a professor at Florida State University who has been investigating how global warming may be altering the strongest storms on Earth, says he would be surprised if South Pacific storms were not growing stronger, like storms elsewhere. But the data is not yet there to prove it.

"We have a pretty solid basis (physical & empirical) for our understanding that ocean heat makes the strongest tropical cyclones stronger," he said. "Empirically it has been shown for the global as a whole and for the North Atlantic. But the signal is hard to see in noisy data, and especially where confounded by a trend toward fewer cyclones."

Although global warming signals may not be present yet, multiple studies have shown that manmade global warming is likely to cause tropical cyclones (including hurricanes and typhoons) to be more intense, on average, than they are today, which means these storms will be more destructive. Manmade warming is also likely to lead to an uptick in the number of extremely intense tropical cyclones in some ocean basins during the next several decades, according to peer reviewed research.

Since sea-level rise is already making cyclones more destructive by giving them a higher launching pad for storm surge flooding, this means that future storms may be an order of magnitude more damaging than what we typically experience today.

As a small, low-lying island nation, Vanuatu is acutely aware of rising sea levels due to global warming. Along with other small island countries, some of which were affected by the same cyclone, Vanuatu has lobbied the U.N. in favor of steep greenhouse gas emissions cuts to reduce the severity of climate change, seeing it as a matter of its very survival as a nation.

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